Maybe I'm just delusional, but I was under the impression that when using DBI that calling using the execute,prepare,fetch technique meant that the table was retrieved piecewise, as in one row at a time. If you were bold enough to use something like fetchall_arrayref() instead, then you would expect the entire thing to appear in RAM. I haven't been able to find any clarification on the internals of DBI with respect to this particular aspect.

I'm doing something pretty simple on a 9M row table, and yet DBI is chomping up a good 300MB+ of RAM if you should let it run that long: 
        use DBI;

        # (Init w. AutoCommit=>1 occurs here)

        # Prepare the SELECT statement...
        my ($s)    = $db->prepare ("SELECT * FROM table");

        # ...and run it.
        my ($s_rv) = $s->execute();

        # Wait patiently, run out of RAM...

        # Presumably, should be able to fetch data and use it here:
        while (my @row = $s->fetchrow_array()) { ... }

[download]
I'm not making it past the $s->execute() statement, and I don't want to make a trip to RAM Depot® for a bulk purchase.

In reply to DBI + 'SELECT *' - Memory Use Galore? by tadman

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.